The goal of this research proposal is to identify virulence factors in Francisella tularensis Schu S4. In nature, F. tularensis causes the zoonotic disease tularemia. F. tularensis is a category A select agent because of its highly infectious nature and the potential ease of its dissemination by aerosolization. Worldwide terrorist activities have resulted in growing concerns about the potential use of F. tularensis as a bioterrorist weapon;in response, the National Institute of Allergy and Infectious Diseases has expanded its biodefense research program in an effort to develop new F. tularensis therapeutics and vaccines. The long-term goal of the proposed research is to identify novel targets for the development of therapeutics for the treatment of tularemia. We will use a genetic approach to identify F. tularensis genes that are specifically expressed during growth in host cells. In accordance with our research goals, three scientific aims are proposed. In specific aim 1 a genomic library will be constructed. In specific aim 2 the genomic library will be screened for in vivo expressed genes and in specific aim 3 null mutants in in vivo expressed genes will be tested in an animal model of tularemia. The results of the proposed work will provide numerous leads for drug discovery, cell biology experiments, and microbiological experiments. PUBLIC HEALTH RELEVANCE: This research project is focused on defining the mechanism by which Francisella tularensis causes the disease tularemia.